792 EVOLUTION AND CONSERVATION Part VI 



understanding of processes that have been investigated since Darwin's time, 

 especially inheritance. Darwin himself was aware of the gaps in knowledge 

 and very wisely pointed them out. One of the finest results of his theory has 

 been the investigation it has set in action. Among the results is the clearer 

 understanding of heritable changes and the ways by which they are passed on 

 from one generation to another. These are discussed in "The Physical Basis of 

 Heredity" (Chap. 20) under "Changes in the Genes — Mutations" and other 

 topics. Now it is known that mutations (changes) occur in genes (the physical 

 units of heredity), and that the chromosomes which contain them may be 

 rearranged. This alters the assortment of genes and hence the characteristics 

 that are passed on to further generations. Darwin knew nothing of all this 

 but he suspected that there was much to be discovered. 



Conservation 



Humanity is facing two very old problems, living with itself and living with 

 its natural surroundings. Conservation is one way of working out these prob- 

 lems, an appreciation and intelligent care of living things and their environ- 

 ments. It is applied Ecology (Fig. 38.10). 



Conservation brings many rewards. The rarest of them is the interest and 

 enjoyment of unspoiled landscapes and the plants and animals growing in their 

 natural places and in relationships, made right by ages of trial. Humanity 

 created civilization out of the wilderness. Now that the wilderness is almost 

 gone, we are beginning to be lonesome for it. We shall keep a refuge for our 

 minds if we conserve the remnants. Psychologists suspect this; fishermen 

 know it. 



Writers and speakers discuss food and distribution of food. They discuss 

 the present extraordinary rise of population and ways in which larger popula- 

 tions shall be fed. They calculate the space that may be necessary to raise more 

 wheat and cattle. They do not give enough thought to the quality and quantity 

 of space for human beings, spaces to whet their curiosity and adventure, to 

 show them natural beauty, to give them places that are far from crowds. Con- 

 servation must guard the open spaces. A full stomach is not a cure-all. 



The results of conservation that are best known are concerned with the care 

 and economy of natural resources that are vital to communities, and to agri- 

 culture and industries. An awareness of the importance of saving the grass 

 roots is increasing; fortunately one of its byproducts is the saving of minds. 



Natural Resources 



Natural resources are everything in nature that is used to sustain life. Those 

 called nonrenewable resources include metals, petroleum, gas, and coal, and 

 the energy of the sun, abundant beyond imagination. It has taken ages to pro- 

 duce them and, except for atomic energy, substitutes in any practicable 

 amounts are not available. The program of conservation for such material is: 



